Battery charging method

Abstract

The battery charging method uses a pulsed current alternately taking first and second amplitudes during first and second periods (t 1 , t 2 ). At least one of the parameters, amplitude and duration, of the current during the first period (t 1 ) is automatically servo-controlled as a function of a first value of the slope (P 1 ) of the voltage (U), measured at the terminals of the battery to be charged. The first slope value (P 1 ) is calculated at least at the end of the first period (t 1 ). Likewise, a second value of the slope (P 2 ) of the voltage (U) can be calculated at least at the end of the second period (t 2 ) and at least one of the parameters of the current during the second period (t 2 ) can be automatically servo-controlled as a function of the second slope value (P 2 ). The different parameters of the pulsed charging current are thus continuously servo-controlled as a function of the voltage slope to keep the slope (P) within a range comprised between 1 mV/s and 6 mV/s.

1. Method for charging a battery by rectangular current pulses alternately taking a first amplitude during a first period and a second amplitude, different from the first one, during a second period, method comprising determination of a first slope value representative of the variation of the voltage the battery terminals versus time, from successive measurements, of said voltage during each first period, wherein the first amplitude and the duration of the first period being previously determined, the method comprises servo-control of at least one of the current parameters during the subsequent first periods as a function of said first slope value calculated and compared with a first predetermined range at the end of each first period, the first current amplitude and/or the duration of the first period being modified if the first slope value goes outside the first range. 
   
   
     2. Method according to  claim 1 , wherein the first range is, in absolute value, comprised between 1 mV/s and 6mV/s. 
   
   
     3. Method according to  claim 1 , comprising
 at least two successive measurements of the voltage at the battery terminals during each second period, 
 calculation, from the voltage measurements during the second period, at least at the end of each second period, of a second slope value representative of the variation of the voltage versus time, 
 comparison of the second slope value with a second predetermined range, 
 servo-control of at least one of the parameters of the current during the second period as a function of the second slope value. 
 
   
   
     4. Method according to  claim 3 , wherein the second range is, in absolute value, comprised between 1mV/s and 6mV/s. 
   
   
     5. Method according to  claim 3 , wherein, during each second period, the successive voltage measurements are made at predetermined time intervals, much shorter than the second period, the second slope value being calculated and compared with the second range after each voltage measurement, the second period being interrupted when the second slope value enters the second range. 
   
   
     6. Method according to  claim 3 , wherein the second slope value is calculated and compared with the second range at the end of the second period, the second current amplitude and/or the duration of the second period being modified if the second slope value goes outside the second range. 
   
   
     7. Method according to  claim 6 , wherein, the second current amplitude being zero, the duration of the second period and the first current amplitude are modified if the second slope value goes outside the second range. 
   
   
     8. Method according to  claim 1 , wherein the current parameters are modified so as to keep the mean value of the current amplitude constant during a charging period constituted by a first period and the following second period.